The invention relates to a hydraulic steering device, in particular for vehicles, having a housing in which two sliders are arranged to move relative to one another and together form at least one adjustable throttle, a restoring device for restoring the two sliders to their neutral position being provided, one of the two sliders being driveable and the other of the two sliders being in operative connection with a measuring device. Furthermore, the invention relates to a method for steering a vehicle, in which hydraulic fluid is supplied to steering motor, is passed by way of a steering device and back again, two sliders being mutually displaced in the steering device.
Such a steering device and such a method are known from U.S. Pat. No. 4,759,182. The two sliders are in that case arranged concentrically with respect to one another in the housing. They are mutually rotated during steering, in which case the inner slider can be acted upon by a steering handwheel whilst the outer slider is connected by way of a spring arrangement, which serves as the restoring arrangement, to the inner slider. In this manner a certain relative movement is possible between the two sliders. The neutral position can be achieved, however, only if hydraulic fluid has flowed through the measuring motor and has driven it so that the outer slider is able to track the inner slider. With the known steering device, it is intended to achieve amplification of the hydraulic fluid so that not all of the hydraulic fluid is able to flow through the measuring motor. For that purpose an adjustable throttle is provided parallel to the measuring motor.
Nevertheless, it should also be possible to operate such steering devices even when the pressure source fails. In that case the measuring motor has to be used as an auxiliary pump, which generates the pressure required to control the steering motor. For that reason the adjustable throttle in the flow path that is arranged parallel to the measuring motor has to close at the upper end of the control range. The in itself intended amplification of the hydraulic flow thus disappears just as a large and rapid angle of lock is being effected. It is precisely in critical situations, however, that such an angle of lock is often desirable. If the desired amplification is not forthcoming, this can lead to dangerous situations.